Anti-pulsation control for furnaces and boilers



April 1957 T. c. GRAMIGNA 2,790,603

ANTI-PULSATION CONTROL FOR FURNACES AND BOILERS Filed Jan. 15, 1954 INVENTOR. THOMAS C GRAM/GNA United States Patent "ice ANTI-PULSATION CONTROL FOR FURNACES AND BOILERS Thomas C. Gramigna, Medford, N. l.

Application January 13, 1954, Serial No. 403,760

2 Claims. (Cl. 236-96) This invention relates to a device for automatically controlling pulsations in furnace combustion chambers, such as domestic oil burner furnaces, boilers, and similar equipment.

In modern homes, such as the low, rambling type ranch homes, the furnace stacks are of necessity comparatively short. As a result, there is frequently a column of cold air at rest in the furnace combustion chamber and stack. In homes of this type, equipped with conventional pressure oil burner systems, a pulsation is sometimes experienced within the furnace due to this column of cold air existing throughout the system from the combustion chamber through the stack. Thus, as the burner is started and air is forced into the combustion chamber by the conventional burner blower, this air, in passing through the system up through the stack, is arrested in its passage by this column of cold air with a resultant setting up of a back pressure. A pulsation of this column of cold air ensues, sometimes manifesting itself in violent vibrations throughout the burner. This effect is created by the fact that the column of cold air is substantially at rest within the system, while the blower air is traveling upward at a velocity which is substantially higher than that of the column of cold air. Consequently, upon meeting the air which is at rest, an inertia effect is created which results in a pressure effect or pulsation, which is felt backwardly through the whole system. This condition is further aggravated by what is known as a tight combustion chamber, i. e. one with little or no leaks therein.

Pulsations of this type are extremely undesirable because of the damaging effects of the vibrations produced thereby on the equipment, from a structural point of view. In addition, when such a condition exists in the initial starting of a furnace, the combustion efficiency is materially reduced, as manifested by large quantities of unburnt fuel and a corresponding high rate of fuel consumption.

In view of this condition, it has been the practice in the past, as a means for overcoming this pulsation, to introduce secondary air into the furnace combustion chamber, which secondary air has the effect of stabilizing the flow within the system and equalizing the back pressure efiect created by the pulsation. To introduce this secondary air into the combustion chamber, furnaces have heretofor been provided with manually operated shutters installed in the furnace wall.

While the secondary air has the advantage of aiding in reducing pulsation within the burner system, it has the disadvantage of reducing the combustion efliciency. The combustion efiiciencies have been reduced from as high as 75-80% to as low as 60-65% by the introduction of secondary air. Thus, during the cold starting phase of the burner combustion process, wherein secondary air is introduced to reduce pulsation, the burning eificiency is at a low level. But as the furnace heats up, the column of cold air disappears and the pulsation therewithin substantially ends, so that the introduction of 2,790,603 Patented Apr. 30, 1957 secondary air is no longer necessary. In that event it is important to close the shutters to eliminate this secondary air so as to dispense with the unnecessary reduction of combustion efliciency. It is obvious that a manually operated shutter would require continual attention and regulation to preclude a constant efliciency loss.

It is an object of this invention, therefore, to provide an improved device for introducing secondary air into furnaces and boilers for controlling pulsation there- It is another object of this invention to provide an automatic device for controlling the introduction of secondary air into combustion chambers for eliminating pulsation.

It is a further object of this invention to provide an automatic device for controlling the introduction of secondary air into furnace combustion chambers which device is simple to construct and economical.

Some furnaces are known to pulsate even when hot. Therefore, it is still a further object of this invention to provide an automatic device for controlling the introduction of secondary air into a furnace combustion chamber, which device can be adjusted so as to vary the amount of said air in accordance with the degree of pulsation existing within the furnace.

Various other more detailed objects and advantages of the invention such as arise in connection with carrying out the above-noted ideas in a practical embodiment will in part become apparent and in part be hereinafter stated as the description of the invention proceeds.

The present invention, therefore, comprises a device which is inserted into the furnace wall at the combustion chamber area, which device permits the introduction of secondary air into the furnace during the cold starting phase of combustion, and which automatically and gradually closes as the combustion chamber heats up, thus providing an overall improved combustion efficiency.

For a fuller and more complete understanding of the invention, reference may be had to the following description and the accompanying drawing wherein similar numerals refer to similar parts throughout the several views.

Figure 1 is a diagrammatic view of an oil fired furnace showing the automatic anti-pulsation control of this invention installed in the furnace wall in the area of the combustion chamber.

Figure 2 is an end elevational view of the present antipulsation control device as viewed from the end thereof which extends into the combustion chamber.

Figure 3 is a side elevational view, with parts broken away, showing the various elements of the anti-pulsation control device in assembled relationship, in an open position for admitting secondary air during the cold starting.

Figure 4 is a side elevational view of the device of Fig. 3 in a closed position, for eliminating the introduction of secondary air after the initial cold starting period.

Figure 5 is a sectional view of an adjustable selfseating disk, taken along the line 5-5 of Fig. 3, for closing the aperture of the present device which permits the introduction of secondary air into the combustion chamber.

Referring to the drawing, particularly Figs. 2 and 3 thereof, the anti-pulsation controldevice of this invention is shown therein as consisting of a steel cylindrical member 10 having perforations 11 about the surface thereof at one end, as shown in Fig. 2. A flange member 12 is fixedly secured to the cylindrical member 10 near the end thereof remotefrom the perforations 11, by brazing or 7 Fig. 2, and fixedly attached to such cylindrical member by means of screws 13, is a support bar 14, the said support bar being positioned substantially in the area of the perforations 11. Carried by the support bar 14, in reciprocal relationship therewith, is a shaft 15 which lies along the axis of the cylindrical member 10.

One end of the shaft 15 extends outwardly of the cylindrical member at the end thereof remote from the perforations 11, and the said shaft is provided with screw threads 16 for a portion of its length, as shown in Figs. 3, 4 and 5. Slidably positioned on the shaft at the threaded end thereof is a disc 17 whose function is to control the flow of secondary air into the cylindrical member 10 in a manner which will be described below.

The position of the disc 17 upon the end of the shaft 15 is controlled by the mechanism depicted in Fig. 5. As shown therein, a nut 18 is threadably attached to the shaft 15 and a coil spring 19 encases the said shaft in abutting relationship with said nut 18. At the end of said coil spring 19, remote from said nut, a collar 20 is slidably carried by the shaft 15. The disc 17 is next slidably carried by the shaft 15 in abutting relationship with the collar 20 and an adjustable thumbscrew 21 abuts the disc 17 on the side thereof opposite from the collar 20. It will thus be seen that with the nut 13 in a fixed position the position of the disc 17 may be varied axially along the shaft 15 by a mere manipulation of the thumbscrew 21, turning it so as to force the disk inwardly or outwardly along the shaft, as occasion demands. The disc 17 is forced into engagement with the thumbscrew 21 by means of the pressure exerted thereon by the coil spring 19.

The opposite end of the shaft 15 remote from the threaded end 16 is curved substantially at right angles to the axis of the cylindrical member 10 for a short portion thereof, as shown at 22 in Fig. 2. Carried by this end 22 of the shaft 15 is an angle member 23 which has connected thereto by means of a screw 24 one end of a heat-sensitive bimetallic ribbon 25, the other end of which is fixedly attached to the support bar 14 by means of a screw 26. The bimetallic ribbon 25 is looped in a substantially sine-curve configuration, as shown in Fig. 3, and it will be noted that the said bimetallic ribbon lies in the area of the perforations 11.

In use, the control device is installed in the wall of the combustion chamber so that the perforated end of the cylindrical member 10 extends into the combustion chamber in close proximity with the flame therein, but not in direct contact with said flame, as shown in Fig. l.

The device is fixedly attached to the wall of the combustion chamber by means of screws or other suitable attachment means cooperating with apertures 27 provided therefor in the flange 12.

In operation, during the initial starting phase of the furnace, when pulsation is normally encountered, the position of the disc 17 on the shaft 15 is adjusted by manipulation of the thumbscrew 21 so as to permit the said disk to lie in an open position, as shown in Fig. 3, to permit the entry of air into the cylindrical member 10. The extent of this opening should of course be varied in accordance with the degree of pulsation existing in the particular furnace in which the present device is installed. With this arrangement, when the furnace is initially started and pulsation occurs, secondary air is permitted to enter the cylindrical member 10 and offset the pulsation etfect through the stabilization of flow and the equalization of pressure within the burner system. As the combustion chamber heats up, the heat of combustion, contacting the bimetallic heat-sensitive element 25 through the perforations 11, causes the said heat-sensitive element to expand longitudinally in the direction of the axis of the cylindrical member 10, as shown in Fig. 4. Since this bimetallic element is attached to the shaft 15, the expansion thereof causes a longitudinal movement of the shaft 15 along the axis of the cylindrical member 10 in a direction toward the perforated end of the cylindrical member 10.. This movement causes the disc 17 to seat itself upon the opposite end opening of the cylindrical member 10 which faces the outside of the furnace wall, thus terminating the flow of secondary air into the combustion chamber. In this manner the amount of secondary air entering into the furnace is automatically controlled in accordance with the need for said secondary air, without the necessity of manual adjustment as in the case of a conventional shutter arrangement.

It will be noted that since the disc 17 rides freely on the shaft 15 in slidable engagement therewith, the said disc is self-seating so as to compensate for any distortions of the bimetallic element which may occur due to the intense heat from the combustion chamber. This disc 17 is preferably made from a light metal such as aluminum or the like.

Since some furnaces are known to pulsate even when operating hot, it is possible to adjust the position of the disc 17 along the shaft 15 so that an opening will be provided even when the bimetallic element 25 has expanded so that a small amount of secondary air Will still be permitted to flow into the combustion chamber.

It will be seen from the above description that a simple and economical device is provided for automatically controlling the introduction of secondary air into the furnace combustion chamber for eliminating pulsation therein. This device has a minimum of perishable and re placeable parts and may be installed with relative ease. Furthermore, it is fully automatic in operation so as to dispense with the necessity of continual observation and regulation.

Although the present discussion of this invention has been limited to the above-described preferred embodiment, other variations thereof are possible without departing from the spirit of the invention. It is not intended, therefore, that the invention be limited to the above-described preferred embodiment, but only to the inventive concept as defined by the appended claims.

What is claimed is:

1. An air-inlet device for the Wall of a combustion chamber, said device comprising an open-ended generally cylindrical member adapted to be arranged horizontally on the inner side of a combustion chamber wall and adapted to be mounted on said combustion-chamber wall with one end projecting through the wall to the outer side thereof, said cylindrical member being formed in the region adjacent to its other end with a plurality of through apertures to allow the passage of fluid transversely through said member, a generally horizontally disposed rod arranged longitudinally within said member having one end projecting outward beyond the outer end of said member and mounted therein for longitudinal sliding movement, a closure plate adapted to be arranged vertically on the outer side of said combustion-chamber Wall and mounted on said one rod end for movement with the latter toward and away from the projecting end of said cylindrical member to open and close the latter, and an elongate bimetallic heat-responsive element located in said cylindrical member adjacent to said other end thereof and having its opposite ends connected to said cylindrical member and rod to eflect reciprocation of the closure plate toward closing relation with respect to said projecting cylinder end in response to an increase in temperature in said combustion chamber and away from closing relation with respect to said projetcing cylinder end in response to a decrease in temperature in said combustion chamber.

2. An air-inlet device according to claim 1, in combination with means adjustably mounting said closure plate on said rod, whereby said closure plate may be properly positioned on said rod in correspondence with the operating characteristics of said bimetallic element.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Broad Mar. 5, 1901 Yerrington Apr. 28, 1903 5 Sturges July 29, 1924 White Feb. 3, 1931 6 Spencer June 28, 1932 Toelle Sept. 18, 1934 Derby Feb. 19, 1935 Drew Aug. 20, 1935 Moule Dec. 31, 1940 Shaw Feb. 11, 1941 Scheu June 6, 1944 

